For example, a power generation gas turbine that is a type of a turbo machine is configured to include a compressor, a combustor, and a turbine. The compressor compresses air introduced from an air intake into high temperature and high pressure compressed air. The combustor supplies fuel to this compressed air to produce combustion, thereby obtaining high temperature and high pressure combustion gas (working fluid). This combustion gas drives the turbine and the turbine drives a power generator connected to this turbine.
In the turbine of the gas turbine of this type, a first stage rotor blade and a second stage rotor blade in front stages are short in a blade height direction (a radial direction of a rotary shaft) whereas a third stage rotor blade and a fourth stage rotor blade (a final stage rotor blade) in rear stages are long in the blade height direction (long rotor blades) in light of performance. The turbine rotor blades long in a blade length direction tend to vibrate. To prevent vibrations, tip shrouds are attached to tip ends of the long turbine rotor blades and the tip shrouds of the adjacent rotor blades contact each other, thereby forming an annular shroud. However, when the tip shroud is attached to the tip end of each rotor blade, then the tip end becomes heavier, a centrifugal force acting on the rotor blade at a time of rotation generates a tensile force in a rotor blade main body, and the rotor blade possibly deforms. Therefore, it is desired to reduce the weight of the tip shroud attached to the tip end of each turbine rotor blade.
As solutions to these problems, for example, there are known techniques disclosed in Patent Literatures 1 and 2 mentioned below. In a turbine rotor blade described in the Patent Literatures 1 and 2, ends of tip shrouds, that is, portions in which the tip shrouds contact each other are recessed in the direction of a rotary shaft so as to form an annular shroud, thereby realizing weight reduction.